Several processes are known which may be used for producing 1,4-dicyano-2-butene from butene derivatives and hydrogen cyanide. (1) GB No. 1,384,796 discloses a process for producing 1,4-dicyano-2-butene which comprises reacting 2-butene-1,4-diol with hydrogen cyanide in a gas phase by using a catalyst comprising a cuprous halide supported on silica gel or the like. (2) German Patent No. 2,144,390 discloses a process for producing 1,4-dicyano-2-butene by reacting 2-butene-1,4-diol with hydrogen cyanide in an aqueous phase in the presence of a catalyst comprising cuprous bromide and an alkali metal bromide. (3) U.S. Pat. No. 3,711,527 discloses a process for producing 1,4-dicyano-2-butene by reacting 1,4-diacetoxy-2-butene with hydrogen cyanide in a liquid in the presence of a catalyst comprising a cuprous halide and a non-aromatic amine hydrohalide.
However, the aforesaid processes are all not fully satisfactory from the industrial viewpoint. The process (1) forms a large amount of impurities and gives a low yield. The process (2) shows a poor volume efficiency (that is, the ratio of the amount of the product formed to the total volume of the reaction system). The process (3) shows a low selectivity to the intended product.